Share-Based Compensation - 10Q - Schedule of RSU Share-Based Payment Award Activity (Details) - Restricted Stock Units (RSUs) [Member] - $ / shares	9 Months Ended	12 Months Ended
Sep. 30, 2021	Dec. 31, 2020	Dec. 31, 2019
Number of RSUs
Outstanding at beginning of period (in shares)	45	0	20,366
Granted (in shares)	50,096	177
Vested (in shares)	16,743	132	20,336
Outstanding at end of period (in shares)	33,398	45	0
Weighted Average Grant Date Fair Value
Outstanding at beginning of period (in dollars per share)	$ 13.55		$ 16.44
Granted (in dollars per share)	1.74	13.55
Vested (in dollars per share)	1.74	13.55	16.44
Outstanding at end of period (in dollars per share)	$ 1.74	$ 13.55

The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(iii)(1)
-URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901

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- Definition

The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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- Definition

The number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 10
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-Paragraph 2
-Subparagraph (c)(2)(i)-(ii)
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Per share or unit weighted-average fair value of nonvested award under share-based payment arrangement. Excludes share and unit options.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
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- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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The number of equity-based payment instruments, excluding stock (or unit) options, that vested during the reporting period.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
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- Definition

The weighted average fair value as of grant date pertaining to an equity-based award plan other than a stock (or unit) option plan for which the grantee gained the right during the reporting period, by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash in accordance with the terms of the arrangement.

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